title: Enriched environment and masticatory activity rehabilitation recover spatial memory decline in aged mice.
abstract: BACKGROUND
  To measure the impact of masticatory reduction on learning and memory, previous studies have produced experimental masticatory reduction by modified diet or molar removal. Here we induced spatial learning impairment in mice by reducing masticatory activity and then tested the effect of a combination of environmental enrichment and masticatory rehabilitation in recovering spatial learning at adulthood and in later life. For 6 months (6M) or 18 months (18M), we fed three groups of mice from postnatal day 21 respectively with a hard diet (HD) of pellets; pellets followed by a powdered, soft diet (HD/SD, divided into equal periods); or pellets followed by powder, followed by pellets again (HD/SD/HD, divided into equal periods). To mimic sedentary or active lifestyles, half of the animals from each group were raised from weaning in standard cages (impoverished environment; IE) and the other half in enriched cages (enriched environment; EE). To evaluate spatial learning, we used the Morris water maze.
  
  
  RESULTS
  IE6M-HD/SD mice showed lower learning rates compared with control (IE6M-HD) or masticatory rehabilitated (IE6MHD/SD/HD) animals. Similarly, EE-HD/SD mice independent of age showed lower performance than controls (EE-HD) or rehabilitated mice (EE-HD/SD/HD). However, combined rehabilitation and EE in aged mice improved learning rate up to control levels. Learning rates did not correlate with swim speed.
  
  
  CONCLUSIONS
  Reduction in masticatory activity imposed on mice previously fed a hard diet (HD/SD) impaired spatial learning in the Morris water maze. In adults, masticatory rehabilitation recovered spatial abilities in both sedentary and active mice, and rehabilitation of masticatory activity combined with EE recovered these losses in aged mice.
authors.affiliation: Universidade Federal do Pará/UFPA, Instituto de Ciências Biológicas, Laboratório de Investigações em Neurodegeneração e Infecção, Hospital Universitário João de Barros Barreto, Rua dos Mundurucus, 4487 - Guamá Belém, Pará, Brasil.
authors.forename: Fabíola de Carvalho Chaves de Siqueira
authors.initials: Fde C
authors.lastname: Mendes
authors.forename: Marina Negrão Frota
authors.initials: MN
authors.lastname: de Almeida
authors.forename: André Pinheiro Gurgel
authors.initials: AP
authors.lastname: Felício
authors.forename: Ana Carla
authors.initials: AC
authors.lastname: Fadel
authors.forename: Diego de Jesus
authors.initials: Dde J
authors.lastname: Silva
authors.forename: Thaíssa Gomes
authors.initials: TG
authors.lastname: Borralho
authors.forename: Rodrigo Perez
authors.initials: RP
authors.lastname: da Silva
authors.forename: João
authors.initials: J
authors.lastname: Bento-Torres
authors.forename: Pedro Fernando da Costa
authors.initials: PF
authors.lastname: Vasconcelos
authors.forename: Victor Hugh
authors.initials: VH
authors.lastname: Perry
authors.forename: Edson Marcos Leal Soares
authors.initials: EM
authors.lastname: Ramos
authors.forename: Cristovam Wanderley
authors.initials: CW
authors.lastname: Picanço-Diniz
authors.forename: Marcia Consentino Kronka
authors.initials: MC
authors.lastname: Sosthenes
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight; D004032:Diet; D004195:Disease Models, Animal; D004777:Environment; D008124:Locomotion / Q000502:physiology; D008409:Mastication / Q000502:physiology*; D018782:Maze Learning; D008569:Memory Disorders / Q000534:rehabilitation*; D051379:Mice; D059385:Plyometric Exercise / Q000379:methods*; D013028:Space Perception / Q000502:physiology*; D013550:Swimming; D013997:Time Factors